This invention relates to a method and apparatus for light beam scanning wherein data character distortion following a stop or data line skipping operation due to the inertia of the vertical deflection mirror is compensated for by delaying the video signal generation until the mirror reaches a constant rotational speed.
A COM (computer output microfilmer) is a device for recording the output of a computer directly on a microfilm, and recent COMs employ a laser beam as the scanning light source owing to its high intensity. Mechanical devices such as a rotary multi-surfaced mirror or a vibrating mirror are advantageous as optical deflection means for the scanning beam due to their low optical loss and large deflection angles. For two-dimensionally scanning a light beam the horizontal scanning may be implemented by a rotary multi-surfaced mirror, while for the vertical scanning a vibrating mirror may be employed to successively deflect the scan line to form a raster. Since such mechanical optical deflection devices have inertia, however, it is impossible to abruptly change their rotation speeds. In the vertical deflection of a scan line after a stop of data line skipping operation, for example, it is impossible to quickly change the rotational speed of the vertical deflection mirror and therefore the intervals between the initial scan lines after such an operation are smaller or larger than normal. Accordingly, if character images are recorded on such scan lines they are either compressively or expansively distorted, and thus difficult to read.